Try to determine where the buzz is coming from. Pluck the A string and hold the A string saddle to see if it is buzzing at the bridge. If you can hold the saddle and the note rings clear with no buzz then there's your culprit. It may be a poorly cut nut slot too. a lazy man test (which I am) is to stick a thin strip of paper under the A string in the nut slot and see if that corrects the open string buzz.
If I had to guess though, I'd say it's probably the bridge. Rod will be along with the "I actually know what I'm talking about" answer soon. That's the answer I suck at.
* Rod beat me to the punch.*